1. Field of the Invention
The present invention relates to a telescoping repair fitting for repairing and replacing sections of plastic pipe that have been damaged.
2. Description of Related Art
When a plastic pipeline becomes damaged, it is desirable to replace the damaged portion of the pipeline with just enough pipe to repair the portion that is damaged. However, the length of the repair pipe should be adjustable to: (i) account for inexact cutting of the replacement piece of pipe and (ii) allow room to maneuver the pipe repair fitting into place in a small space, such as a pipe trench.
In one type of pipe repair, known as butt fusion, the ends of the pipe are heated as well as the ends of the replacement piece to fuse the joint. The heater may be inserted between the ends. In order to do so, the existing pipes must be axially displaced to make room for the width of the heater. Accordingly, it will be necessary to distort the existing pipeline axially or move the pipeline from its position.
One problem that arises when pipelines are repaired in a small space is that it is difficult or dangerous to work with a heater to form fusion joints. When natural gas is present, ignition from a spark from a heater must be avoided. In such a situation, there are dangers of burning oneself or a coworker or of igniting flammable vapors. For other types of joints, such as chemical solvent joints, there is a danger that the chemicals are respiratory hazards in small spaces. For other joints, such as elastomeric gasket joints or mechanical compression joints, a small space may make working with these joints very cumbersome.
Therefore, there is a need for a repair fitting having a length which may be adjusted to account for inexact measuring and pipe cutting. There is also a need for a repair fitting which may easily be positioned for attachment to pipeline ends. Still further, there is a need for a repair fitting for which any hazardous activities relating to installation of the repair fitting are performed away from a confined space, such as a pipe trench. It is further desired to provide a repair fitting which can easily be attached to pipelines.
An additional problem may arise when cutting an existing plastic pipeline. Because of thermal conditions, the pipeline may be under axial stress. For example, in one type of pipe, it is known that the pipe expands and contracts 1" axially for each 100 feet of pipeline for every 10.degree. F. change. Cutting the pipeline will release the axial stress, causing the pipeline to move axially even while the repair is being made.
There have been other repair fittings for repairing damaged pipeline sections. Lomelino (U.S. Pat. No. 2,461,828) discloses an extension joint which is telescopically adjustable to sealably connect pipeline ends.
Lyall et al. (U.S. Pat. No. 4,386,796) discloses a telescoping repair fitting having a hollow piston within. A plurality of O-rings surround the piston. One end of the piston is connected to a pipe end while the fitting has a shoulder to receive the other pipe end.
Williams (U.S. Pat. No. 3,594,021) discloses an expansion joint having a transparent first or barrel sleeve in which is telescoped a piston or second sleeve. A pair of O-rings around the piston sleeve provide a seal.
Kutschke (U.S. Pat. No. 4,049,480) discloses a method and apparatus for connecting a pair of abutting pipe sections. The pipe ends are attached together by applying tape around a circumference, a sleeve is moved to position overlapping the section intersection, and the annular space closed by gaskets and tape. A settable polyurethane foam is injected into the annular space.
Zimmerman (U.S. Pat. No. 4,687,232) discloses a pipe coupling having a joint housing which may be rotated or may be moved longitudinally. A piston pipe moves longitudinally in the housing with a seal between O-ring and piston wall of the joint housing.
Guilloteau (U.S. Pat. No. 4,836,581) discloses an adaptable length joint with a flange on each pipe having a spherical bearing surface.
Anderson, Jr. (U.S. Pat. No. 4,932,686) discloses a telescoping connector having a first tubular member allowing axial movement and a threaded connection.
Bryant et al. (U.S. Pat. No. 5,082,313) discloses an expansion joint telescoping members having outside threaded ends.
For additional background information concerning plastic pipe fittings, reference may be had to the following previously issued United States patents:
______________________________________ U.S. Pat. No. INVENTOR(S) TITLE ______________________________________ 4,804,209 Fischer PLUMMER'S UNION 4,810,008 Brodie METHOD AND APPARATUS FOR REPAIRING LAWN SPRINKLER SYSTEMS 4,946,213 Guest TUBE COUPLINGS 5,024,469 Aitken et al. ADJUSTABLE LENGTH PIPING UNION 5,082,313 Stine EXPANSION JOINT FOR CONDUIT FOR CABLES 5,442,482 Baddour WELDLESS PIPE REPAIR APPARATUS AND METHOD 5,509,698 Habicht AXIALLY EXTENDIBLE CONDUIT 5,692,785 Wartluft et al. PLASTIC PIPE COUPLER WITH INTERNAL SEALER ______________________________________